Transmission "shudder" 04 YukonXL

Zimtok · September 1, 2015

Cruising along at say 50-60mph as I go up a slight hill the transmission will start this shuddering like it is trying to decide whether to down shift or not.

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efritz · September 2, 2015

Any trouble codes?

Zimtok · September 2, 2015

NO warning indicator on the cluster.

I haven't attached my scanner yet.

I forgot to mention this transmission has the Tow button on the gear selector.

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Zimtok · September 3, 2015

NO codes come up in my OBDII scanner.

The only thing I can find with a general search online is some mention a shudder that may be caused by the torque converter.

That seems possible. but what do you guys think?

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efritz · September 3, 2015

Do the RPMs noticeably increase? If this happens in OD, you likely have one of two problems: either your TC clutch is toast or your 2-4 band is, possibly 3-4 clutches, maybe even forward clutches. The way to tell whether it is the Torque converter clutch or an internal clutch is by leaving your foot on the gas when it happens and very lightly pressing the brake with the other foot as this will release the TC clutch and make it stop shuddering if it is slipping. Either way, it is likely time to R&R and get a new TC, especially if this unit has some miles on it. Hey, at least every time you have to rebuild something, it is a chance to put performance parts in

Zimtok · September 4, 2015

No increase in RPM's when shuddering.

It does seem to stop shuddering when the brake peddle is slightly pressed, and I thought I noticed an increase in RPM's sometimes when I did the brake peddle test.

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anumber1 · September 4, 2015

That simple observation points to a failing torque converter lockup clutch.

efritz · September 4, 2015

Yep, likely TC clutch is not locking up fully, however, the problem is likely hydraulic in the transmission as the TC clutches on these are woven carbon fiber and rarely fail. Could be a simple in pan fix, such as a leaky TC regulator valve or failing lockup solenoid. Still is a chance that the TC clutch itself has failed. It's worth a try to install the PWM bypass made by FITZALL, sometimes it alleviates these problems. It's a simple drop the valve body and pound in a replacement valve plug job.

wilsonz71 · September 6, 2015

Sure sounds like a tc shudder. I just had one let go. Tried a lockup solenoid like my trans builder suggested, but it ended up being the tcc in the converter itself. Is your converter locking up properly?

Zimtok · September 8, 2015

I believe it is locking up.

I only get the shudder when a light load is put on it, if it down shifts there is no shudder.

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anumber1 · September 8, 2015

Yeah. No shudder when it down shifts because that is when it is not locked up.

The tc should only be locked in high gear at low load.

oldmann · September 8, 2015

Sounds to me like it is going from v8 to v4 mode

SouthCo · September 8, 2015

Sounds to me like it is going from v8 to v4 mode

No cylinder shut down on '04 Yukons.

Zimtok · September 9, 2015

Yep, likely TC clutch is not locking up fully, however, the problem is likely hydraulic in the transmission as the TC clutches on these are woven carbon fiber and rarely fail. Could be a simple in pan fix, such as a leaky TC regulator valve or failing lockup solenoid. Still is a chance that the TC clutch itself has failed. It's worth a try to install the PWM bypass made by FITZALL, sometimes it alleviates these problems. It's a simple drop the valve body and pound in a replacement valve plug job.

PWM bypass?

What is it, and where do I get one?

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